Elastomeric joint seal

ABSTRACT

An inner form for a concrete mold assembly includes adjoining retractable wall sections, and a substantially non-porous, deformable elastomeric joint seal between the wall sections. A retracting force applied to the wall sections exerts pressure on the seal to squeeze the seal and thereby shrink the size of the inner form in preparation for the lifting of a concrete casting over the form. During casting operations, the outer surface of the joint seal is flush with the outer surfaces of the adjacent wall sections. The joint seal is configured so that the pressure applied by the edges of the wall sections is induced eccentric to the centroid of the seal to substantially prevent the outer surface of the seal from bulging beyond the outer surfaces of the adjacent wall sections. This prevents the seal from being abraded away by the concrete casting when it is lifted over the form.

' 22' 1 Filed:

United States Patent 1191 Loeber [5 1 ELASTOMERIC JOINT SEAL [75] Inventor: Frederick W. Loeber, Downey,

- Calif.

[73] Assignee: Ameron lnc., Monterey Park, Calif.

May 24, 1972 [21] Appl. No.: 256,306

[52] US. Cl 249/1'79, 249/152, 249/l80, 249/183 [51] Int. Cl 'B28b 7/30 [58] Field of Search 249/183, 178, 179, 180,

1 [56]. References Cited I UNITED STATES PATENTS 150,333 4/1874 Leverty 249/183 x- 2,942,320 6/1960 Vos .t 3,567,173 3/1971 An inner form for a concrete'mold assembly includes Peterson 24 9/l83.

1111 3,815,864 1451 June 11,1974

- ime tem km het kazew .5 Attorney, Agent, or Firm-Christie, Parker & Hale ABSTRACT adjoining retractable wall sections, and a substantially non-porous, deformable elastomeric joint seal between the' wall sections. A retracting force applied to the wall sections exerts pressure on the seal to squeeze the seal and thereby shrink the size of the inner form in preparation for the lifting of a concrete casting over the form. During casting operations, the outer surface of the joint seal is flush with the outer surfaces of the adjacent wall sections. The joint seal is configured so .that the pressure applied by' the edges of the wall sections is induced eccentric to the centroid of the seal to substantially prevent the outer surface of the seal from bulging beyond the outer surfaces of the adjacent wall sections. This prevents the seal from being abraded 'away by the concrete casting when it is lifted over the form.

5 Claims, 10 Drawing Figures PATENTEDJUH 1 1 I974 SHEET 2 (IF 4 PATENTEUJUH] I I974 sum 30$ 4 .1 ELASTOMERIC JOINT SEAL BACKGROUND OF THE INVENTION This invention relates to the art of concrete casting, and more particularly to a deformable elastomeric joint seal. for use between retractable wall sections of an inner form of a concrete mold assembly.

In the art of casting generally hollow concrete products, fluidous concrete ordinarily is poured over a wallforming retractable core. An expandable outer form is disposed around the periphery of the core, and the natural force of gravity acts on the fluidous concrete to fill the space between the outer form and the core. After the concrete cures, the outer form is removed, and the core is then retracted so the interior of the casting can be stripped from the core.

This invention provides a deformable elastomeric joint seal to be disposed between retractable wall sections of an inner form or core. In use, as the wall sections are retracted, they squeeze the seal, which enables the wall sections to move toward each other and thereby shrink the size of the core. The concrete casting is then lifted over the top of the core.

In the manufacture of pre-cast concrete modular building units, such as steel-reinforced concrete rooms for use in construction of multi-story dwelling units, the concrete casting to be lifted weighs-as much as 30 tons, and is lifted through about 8 feet of travel to clear the core.

Likewise, in the manufacture of concrete pipe, it is necessary to compress the inner form for removal after the concrete has hardened.

Preferably, the joint seal is made of a tough nonporous elastomer, such as synthetic rubber having a hardness of 40 to 60 on the Shore A Durometer scale. Sponge rubber is not preferred, because it becomes permeated'by the cement slurry, and is notrugged enough to withstand repeated use. The preferred elastomer is substantially volumetrically incompressible, and therefore bulges when deformed by thewall sec tions of the core. If the seal bulges beyond the outer surfaces of the adjacent wall sections, it can be abraded away shortly during use when the heavy concrete castings are lifted over the core. Such abrasion eventually would cause the outer surface of theseal to be curved concave inwardly during subsequent molding operations with the fluidous concrete. After the concrete cures, considerable hand grinding would be required to remove ridges formed on the inner walls of the casting by the abraded seal.

SUMMARY OF THE INVENTION This invention provides an elastomeric joint seal which does not bulg'e beyond the outer surface of the wall sections of an inner form, and therefore does not abrade away when a casting is removed from the form.

. sections to squeeze theseal between them to move the wall sections toward each other. The cross-sectional shape of the joint seal is configured so that the pressure applied by the edges of the wall sections is induced eccentric of the centroid of the seal, so that the outer surface of the seal is substantially prevented from bulging beyond the outer surfaces of the-wall sections.

In a preferred form of the invention, the joint seal is configured such that a minor portion of the mass of the seal is disposed between the pressure-applying edges of the wall sections. A major portion of the seal protrudes from the innermost pressure-applying edges toward the interior of the coresPreferably, the protruding major portion of the seal is spaced from the adjacent edges of the wall sections, and therefore is not confined in its movement by the wall sections.

When the eccentric loading is applied'to the seal, mass flow is induced away from the confined minor portion of the seal toward the unconfined protruding major portion. Thus, the protruding major portion of the seal accommodates the mass flow from the part of the seal which is squeezed between the wall sections, and therefore bulges toward the interior of the core.

The spacing between the sides of the protruding portion of the seal and the adjacent edges of the wall sections is such that the protruding portion does not come in contact with the wall sections when the seal is being squeezed by them. Thus, the major portion of the seal remains an unconfined flowable mass capable of accepting mass flow from the portion of the seal being squeezed between the wall sections. Since mass flow is induced toward the interior of the form, the seal does not bulge beyond the outer surfaces of the adjacent wall sections. As a result, the seal is not abraded away by the casting as the casting is lifted over the form. This extends the life of the seal, and substantially avoids the formation of irregularities, or ridges, in the inner walls of the casting.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view showing an elastomeric joint seal between wall sections of a retractable inner form for concrete molds;

FIG. 2 is a fragmentary sectional elevation view taken on line 22 of FIG. 1;,

FIG. 3 is a fragmentary schematic sectional elevation view showing the cross-sectional shape of the joint seal prior to retraction of the wall sections of the core;

FIG. 4 is a fragmentary schematic sectional elevation view showing the joint sealof FIG. 3 at an intermediate stage of the retracting operation;

FIG. 5 is a fragmentary schematic sectional elevation view showing the joint seal of FIG. 3 at a final stage of the retracting operation;

FIG. 6 is a fragmentary elevation view, partly in sec tion, showing the configuration of the joint seal at a corner of the form prior to retraction of the wall sections of the form;

FIG. 7 is a fragmentary elevation view taken on line DETAILED DESCRIPTION or THE PREFERRED EMBODIMENTS Referring to FIG. 1, a generally rectangular retractable inner form or core assembly forms a hollowed interior of a concrete casting (not shown in FIG. I). The casting is formed between the core-and an expandable outer form (not shown) spaced from the outer walls of the core and extending around the periphery of the core. During casting operations, fluidous concrete is poured between the core and outer form. After the concrete is cured, the outer form is removed from the casting. The core is then retracted inwardly to shrink its size so the casting can be lifted over the core.

The retractable core comprises a generally rectangular box having an opening 12 in its bottom to allow access to its interior. The end walls and the side walls of the box'are each divided in half, and the top of the box is divided into four equal parts, with the lines of separation dividing the box symmetrically into four equal quadrants 14. Each quadrant is a separate wall-forming corner section having a separate end wall section 16, side wall section 18, and top panel section 20.

The space between quadrants is sealed by a narrow, deformable elastomeric joint seal 22. The seal follows the lines of separation of the box. Thus, the seal is X- shaped when the box is viewed in plan view, and it follows the vertical centerline of eachside wall and end wall of the box.

FIG.- 2 shows atypical cross-sectional view of joint seal 22 mounted between adjacent wall sections of adjacent quadrants. By way of example, FIG. 2 shows the seal mounted between the adjacent edges of top panels of the rear pair of quadrants viewed in FIG. 1. The seal is mounted in an .identical fashion between the edges of end walls 16 and side walls 18 of the core. The edges of the seal are keyed in corresponding marginal grooves 24 formed in the edges of the quadrantsaThe seal has a pair of opposed, outwardly projecting, elongated shoulders 26 along its sides. The shoulders are fitted into corresponding grooves in each pair of adjacent quadrants.

The shoulders make a tight friction fit in their corresponding grooves. Prior to use of the core, the wall-sections of the quadrants are retracted inwardly toward the center of the core to an operating point at which a slight pre-compression force is constantly applied to the seal. FIG. 2 shows the seal at its operating point in readiness for pouring of the concrete. The seal is maintained in a non-bulging condition, with its outer surface 28 being flush with the outer surfaces of the adjacent quadrants. The pre-compression force prevents the cement slurry from penetrating the area between the seal and the edge of each wall section.

During casting operations, fluidous concrete is poured over the core to form a casting 30 having a hollowed interior, the interior walls of the casting being formed by the wall sections of the core. After the con crete cures, the walls of the core are retracted to shrink the size of the core to allow the casting to be lifted over it. Preferably, the core is retracted by a retracting mechanism (not shown) in the interior of the core. The preferred retracting mechanism pulls the interior corners of each quadrant toward the center of the core to compress joint seal 22 substantially uniformly along its entire length. Thus, each end wall section 16 and side wall section l8 moves inwardly from the interior walls of the casting a substantially uniform distance. This allows the casting to be easilylifted over the top of the core. I

Elastomeric joint seal 22 is made of a non-porous, deformable elastomer, such as synthetic rubber. The preferred elastomer is of 40 to Shore A Durometer hardness, oil-resistant neoprene rubber. The preferred hardness is 50 Shore A Durometer. Such a material is rugged during use, and thus is able to withstand the constant compression and expansion to which it is subjected. It is also impervious to attack by the form oil and cement slurry with which it comes in contact. Porous or sponge rubber is not desired, because it is not rugged, and the pores of such material become permeated with the cement slurry, which would cause the seal to eventually break down during use. The preferred non-porous hard rubber elastomer is substantially volumetrically incompressible, i.e., the seal is resilient, or

deformable, but its volume remains substantially con stant when it is deformed. Thus, the seal bulges when compressed between the edges of the wall sections.

The particular cross-sectional shape of .the joint seal shown in the drawings prevents the seal from bulging outwardly beyond the exterior of the wall sections when the seal is squeezed by the wall sections. As shown best in FIGS. 3 through 5, the cross-sectional configuration of the seal includes a minor portion 32 which is confined between pressure-applying edges of the wall sections, and a major portion 34 which protrudes toward the interior of the core and therefore away from the inner wall of casting 30.

The confined minor portion of the seal has opposed short outer edges 36 which project away from shoulders 26 and intersect the non-bulging outer surface 28 at the corners of the seal. Edges 36 are compressed between corresponding pressure-applying edges 38'of the wall sections. The minor portion 32 also includes shoulders 26, which are disposed in the pressure-applying grooves 24 of the wall sections, and the portion of the seal between the shoulders.

The protruding major portion hasouter edges 40 which are spaced from corresponding adjacent nonpressure-appl'ying edges 42 of the wall sections. The spacing between edges 40 and wall section edges 42 is such that even when the seal is compressed to its maximum amount, as shown in FIG. 5, edges'40 of the seal are substantially prevented from contacting edges 42 of the wall sections. The purpose of this arrangement-is described in detail below.

FIGS. 3 through 5 show schematic views of the crosssectional area of the joint seal, in whichgrid lines 44 on the seal illustrate the flow characteristics of the rubber in the seal when the seal. is compressed from its initial casting position (FIG. 3), through an intermediate position (FIG. 4), to a final stage (FIG. 5) in'which maximum pressure is applied to the seal by the wall sections. When the wall sections are retracted, they apply pres sure at a point eccentric to the centroid of the seal. The

eccentric loading is on the side of the centroid occupied by concrete casting 30, and this loading causes the rubber in the seal to flow toward the protruding major portion 34 of the seal. This prevents the seal from bulging beyond the plane of the outer surfaces of the adjacent wall sections. Grid lines 44 become distorted when the seal is compressed, and thereby illustrate these flow characteristics of the rubber in the seal.

When eccentric loading is applied, a non-uniform internal pressure distribution builds up in the seal. The rubber in the confined minor portion of the seal experiences relatively high pressure build-up during such loading. The rubber in the protruding major portion 34 of the seal is a freely flowable mass, and the internal pressure build-up in this area is relatively low during loading. Thus, the rubber in minor portion 32 flows to the low pressure zone during loading. The distorted grid lines show how this mass flow takes place. The rubber in the confined high pressure area of the seal must flow somewhere when loading is applied, and the eccentric loading directs the flow of rubber in the confined pressure-receiving area toward the protruding low pressure area of the seal. Since the latter portion of the seal is a freely flowable mass, it is capable of accepting the mass of rubber flowing from the eccentri cally loaded area of the seal. Thus, as the minor portion 32 becomes progressively squeezed between the pressure-applying edges of the wall sections, the protruding portion of the seal progressively expands in size to accommodate the mass flow from the squeezed portion of the seal.

Thus, the eccentric loading of the seal induces flow away from the inner walls of the concrete casting 30, and'therefo're prevents outer surface 28 of the seal from bulging beyond the plane of the outer surfaces of the wall sections of the core.

As explained previously, the protruding major portion of the seal is shaped so its edges are prevented from coming into contact with the adjacent inner edges 42 of the wall sections, when the wall sections are retracted their maximum amount (shown in FIG. 5). If the walls come in contact with protruding portion 34, internal pressure will build up in the protruding portion, which would then impair its free flow characteristics. This would prevent the protruding portion from freely accommodating the rubber flowing from the pressure-receiving minor portion, and could cause at least aportion of outer surface 28 to bulge beyond the' plane of the adjacent wall sections.

When the seal is squeezed between the wall sections, protruding portion 34 expands volumetrically. Thus, lengthwise expansion of this portion of the seal must be accommodated at the corners of the inner core. FIGS. 6 through 9 show a preferred method of accommodating lengthwise-expansion. A pair of slotted areas 46 are formed in protruding portion 34 near each corner of the core.

As shown best in FIG. 8, lengthwise expansion of protruding major portions 34 fills the spaces provided by I slotted areas 46. This prevents internal pressure buildup in the protruding portion of the seal, and thereby,

maintains the free flow characteristics of the seal to prevent the seal from bulging beyond the plane of the wall sections.

While the use of the joint seal shown and described above is a preferred one, it is contemplated that, alternately, the seal can be used in other types of retractable mold assemblies. Thus, by way of example, FIG. 10 shows a mold assembly 50 used in the vertical method of making a concrete pipe 52. The mold assembly includes a vertically disposed, cylindrical outer form or shell 54, and a cylindrical inner form or core 56 disposed concentrically inside the outer form. Outer form 54 has a longitudinal split 58, and the split is sealed by a suitable elastomeric seal 60 between opposed L- shaped flanges 62 rigidly secured to opposite sides of the split. The flanges are releasably secured together along the length of the split by suitable longitudinally spaced apart fastening means, such as bolts 64.

The inner form includes a longitudinal split 66 which is sealed by elastomeric joint seal 22. Seal 22 has an arcuately curved outer surface 67 which is continuous with the circumference of the outer wall of inner form 56. Shoulders 26 of the seal are seated in longitudinally extending opposed slots 68 formed between the interior wall of the inner form adjacent the split and opposed recessed portions of a pair of gate members 70 extending the length of the inner form along both sides of the split.

The inner form is retracted by a suitable retracting mechanism which bridges gate members 70. By way of example, FIG. 10 shows a retracting mechanism which includes an L-shaped crank arm 72, the corner of which is pivotally secured to an apertured lug 74 rigidly secured to one gate member, and a lever arm 76 having one end pivotally secured to a lug 78 on the other gate member. The other end of lever arm 76 is pivotally secured to the crank arm leg which bridges the seal. Preferably, several such retracting mechanisms are spaced apart along the length of the seal. An elongated rod 80 extending the length of the form is welded to the free end of each crank arm, and in use the rod is rotated, by

suitable drive means (not shown), in the direction of the arrow shown in FIG. 10 to pivot the crank arm, and thereby move the gate members toward each other to compress the seal and retract the inner form.

Thus, the elastomeric seal is compressed to permit shrinking of an inner form without excessive wear on the seal as a concrete casting is lifted over the form. Moreover, the seal substantially prevents irregularities from being formed in the inner walls of the casting as the concrete cures, which substantially avoids the need for hand grinding to remove ridges and the like otherwise formed inside the casting.

I claim:

1. A retractable inner form for a concrete mold assembly comprising a pair of adjacent wall sections bordering a hollow interior of the form and having corresponding outer surfaces arranged to form the inner contour of a concrete casting, the wall sections also having corresponding inner surfaces defining the hollow interior of the form, and laterally spaced apart pressure-applying edges each extending between a corresponding outer surface and a corresponding inner surface of the wall sections,

a substantially non-porous, deformable elastomer between the pressure-applying edges of the wall sections forming a joint seal,

the joint seal having a front surface extending substantially continuous with the outer surfaces of the adjacent wall sections, and opposite side edges extending inwardly from the front surface of the seal toward the hollow interior of the form, each side edge having'a pressure-receiving portion engaged with a corresponding pressure-applying edge of the wall sections, whereby when a retracting force is applied to the wall I sections of the inner form, pressure is exerted on I the pressure-receiving portions of the joint seal to squeeze the seal and reduce the size of the inner I form, the joint seal being of such cross-sectional shape and being engaged with the wall sections such that 'the pressure applied by the edges of the wall sections is induced eccentric to the centroid of the joint seal at such points of contact that a minor portion of the joint seal cross-sectional area extends between the front surface of the seal to the'pressure-receiving portions-thereof, and a major portion of the joint seal cross-sectional area extends from' said pressure-receiving portions inwardly toward the interior of the form remote from the front surface of the seal, the opposite side edges of the joint seal majorportion being laterally spaced from the adjacent pressure-applying edges of the wall sections during normal ,retraction of the form to accommodate inward expansion of the joint seal when the wall sections are retracted so that the front surface of the 5. Apparatus according to claim 1 in which the inner I form also has a pair of adjacent transverse wall sections, each of which intersects a corresponding one of r the other wall sections to form a corner of the form,

and including a transverse joint seal disposed between adjacent spaced apart edges of the transverse wall sections, the transverse joint seal being continuous with the other joint seal at the corner formed by the wall sections, and in which a separate lengthwise portion of the major'cross-sectional area of each joint seal is removed at a point adjacent the corner of the form to accommodate lengthwise expansion of each seal'when the wall sections are retracted. 

1. A retractable inner form for a concrete mold assembly comprising a pair of adjacent wall sections bordering a hollow interior of the form and having corresponding outer surfaces arranged to form the inner contour of a concrete casting, the wall sections also having corresponding inner surfaces defining the hollow interior of the form, and laterally spaced apart pressureapplying edges each extending between a corresponding outer surface and a corresponding inner surface of the wall sections, a substantially non-porous, deformable elastomer between the pressure-applying edges of the wall sections forming a joint seal, the joint seal having a front surface extending substantially continuous with the outer surfaces of the adjacent wall sections, and opposite side edges extending inwardly from the front surface of the seal toward the hollow interior of the form, each side edge having a pressure-receiving portion engaged with a corresponding pressure-applying edge of the wall sections, whereby when a retracting force is applied to the wall sections of the inner form, pressure is exerted on the pressurereceiving portions of the joint seal to squeeze the seal and reduce the size of the inner form, the joint seal being of such cross-sectional shape and being engaged with the wall sections such that the pressure applied by the edges of the wall sections is induced eccentric to the centroid of the joint seal at such points of contact that a minor portion of the joint seal cross-sectional area extends between the front surface of the seal to the pressure-receiving portions thereof, and a major portion of the joint seal crosssectional area extends from said pressure-receiving portions inwardly toward the interior of the form remote from the front surface of the seal, the opposite side edges of the joint seal major portion being laterally spaced from the adjacent pressure-applying edges of the wall sections during normal retraction of the form to accommodate inward expansion of the joint seal when the wall sections are retracted so that the front surface of the seal is substantially prevented from bulging beyond the outer surfaces of the adjacent wall sections.
 2. Apparatus according to claim 1 in which the joint seal is substantially volumetrically incompressible.
 3. Apparatus according to claim 1 in which the pressure-receiving portions of the joint seal include opposed shoulders fitted in cooperating grooves in the pressure-applying edges of the wall sections.
 4. Apparatus according to claim 1 in which the elastomer is made of oil resistant neoprene of 40 to 80 Shore A Durometer hardness.
 5. Apparatus according to claim 1 in which the inner form also has a pair of adjacent transverse wall sections, each of which intersects a corresponding one of the other wall sections to form a corner of the form, and including a transverse joint seal disposed between adjacent spaced apart edges of the transverse wall sections, the transverse joint seal being continuous with the other joint seal at the corner formed by the wall sections, and in which a separate lengthwise portion of the major cross-sectional area of each joint seal is removed at a point adjacent the corner of the form to accommodate lengthwise expansion of each seal when the wall sections Are retracted. 